How to Worm Farm

A worm farm will take care of your kitchen scraps and turn them into some of the richest organic fertiliser known to man. At the same time you’ll be breeding up a population of worms that can be introduced to areas of your garden, or used to start new worm farms for your friends and family.

What are Worms?

Earthworms and composting worms are slimy things which live in the soil and feed on decomposing organic matter. Worms burrow as they move, making tunnels through the earth, and leaving behind castings, which are a rich organic fertiliser.

What is a Worm Farm?

A worm farm is a container or series of containers which acts as a home and ideal breeding environment for composting worms. All worm farms enable food to be added, and worm castings (vermicompost) to be retrieved for use as fertiliser. Some worm farms are designed to separate and capture worm urine as well, for use as a liquid fertiliser.

How to Make a Simple Worm Farm

Ask at your local fruit & veg market for empty polystyrene (styrofoam) boxes. They’re often used to transport broccoli.

Cut one of the boxes to half it’s height.

Poke holes in the other box’s bottom.

Put the second box on top of the first box, and you’ve got a worm farm!

The worms and food go in the top, and worm urine and excess moisture will drip into the bottom box.

You can also use the polystyrene lid as a lid for your worm farm, but you’ll have to poke lots of small holes for air – small enough that flies can’t get in.

Keep your worm farm out of the sun, inside if you like – somewhere handy to the kitchen, where you can add to it easily.

How to Start a Worm Farm

Collect food scraps, including rotting fruits and vegetables, but excluding meat, dairy, oils and salt. Worms will tolerate most foods, and work optimally with a varied diet.

Get some composting worms, from a fellow worm farmer or a local supplier. They should be red in colour, and it’s best if there’s a mix of eggs, babies and adults.

Lay a sheet of wet newspaper down on the bottom of your worm box. This will help prevent worms falling through your holes, but it should be thin enough that moisture can drain through.

Wet and shred plain cardboard or newspaper (as much as you like) and toss it in. This will act as a bedding for your worms, and they will eventually eat it.

Spread your worms over the cardboard. They don’t like sunlight, and you should see some retreating into the cardboard.

Shred some wet newspaper or cardboard to cover them. This will protect them from your scraps until they’re ready. A thin layer is all that’s necessary.

Spread your food scraps and other worm food over the top. The worms will venture out to eat, and retreat to their bedding.

Sprinkle a handful of soil over the food scraps. Worms are used to keeping a bit of grit in their guts to help break up food. They will take it as they need it.

Shred a final layer of wet newspaper or cardboard, and cover the food scraps. This will later become the new bedding for your worms.

Keep the top layer damp, and the worms will have all that they need. If excess moisture builds up, it will drip through the holes into the bottom box. This can be used as an organic liquid fertiliser for the garden.

How to Feed a Worm Farm

I recommend collecting a good mix of kitchen scraps and other worm food before adding to your worm farm. The worms will take time to get through your initial inputs, so there’s time to collect a variety of materials for them. If you’re producing lots of food scraps, consider composting them, or starting another worm farm.

Check that the top layer of the worm farm is still damp. This will become their new bedding once they’ve eaten the original stuff.

Spread your kitchen scraps and other worm food over the top.

Sprinkle a handful of soil over the food scraps.

Shred a new top layer of wet cardboard or newspaper.

How to Empty a Worm Farm

When your worm farm is full, and almost all the materials have been consumed, it’s a good time to empty and restart your worm farm.

Lift the full box off the bottom box, and place it on the ground. If there’s liquid in the bottom box, you can use it as a liquid fertiliser (dilute it 50/50).

Scoop any uneaten scraps out of the worm farm, into a bucket.

Tip the box out, on a large sheet of cardboard, and spread the castings and worms out about 2 inches thick. Worms don’t like sunlight, and they’ll retreat from the top 1 inch of castings, down to the bottom inch.

While you’re waiting, shred some wet cardboard or newspaper into the bottom of the worm farm box, as a fresh bedding to start the farm again.

Once the worms are out of sight, scrape off the top inch of castings and collect them in a bucket. You can apply these straight to your garden.

Pick up opposing edges of the sheet of cardboard, so that it bends and forms a ‘V’ shape. Pour the worms and remaining castings into your worm farm box, on top of the fresh bedding. If it’s too heavy, scoop up the worms instead.

Shred another layer of wet cardboard or newspaper to cover them, then add the uneaten scraps, along with any fresh worm food and a handful of soil.

Cover again with shredded wet cardboard or newspaper.

You should notice each time you empty your farm, the worm population has increased. This is good news. Once their numbers are booming, consider starting another worm farm, a worm trough, a worm tower, a worm bag, or worm stations around your garden.

Frequently Asked Questions

Why worm farm?

Worm farming is an easy way to manage your waste and create fertiliser for your garden. Making worm farms is easy, and can be done for free, done as classroom projects, and given as gifts. Worm farms are also suitable for balconies and people who are renting their home.

What other designs for worm farms are there?

Most purchased worm farms use a tiered/multi-layered system of containers, which encourages worms to move up through the layers, vacating the castings at the bottom. These can be made using three or more plastic storage boxes.

Bathtub worm farms make good use of an old tub. Chock it up on some bricks, lay down some fly screen mesh on the inside so the castings are easy to remove, and make a couple of lids. The drain hole still works and the lids can double as a work bench.

Fridge worm farms are another alternative. Lay an old fridge on it’s back so that the doors open like a chest. Start your worms at one end, and gradually encourage them across to the other. Take castings from behind them as they move back and forth. Remove parts of the door seal so air can get in.

How many worms do I need?

You don’t need a lot of worms to start a worm farm, but the less you have, the longer you’ll have to wait for them to consume your scraps. In suitable environments worms can double their population every 6 weeks. If you want to get off to a flying start, buy a starter box of worms (approximately 1000 eggs, babies and adults).

Do I need to flush my worm farm?

No. Flushing worm farms with water is a popular practice, and is useful if you want to use liquid fertiliser. However, worms will operate well in a worm farm that is only kept damp, and which allows for any excess liquid to drain. By not flushing your worm farm, you are keeping nutrients in the castings, and so you are making the richest fertiliser possible.

How often do I need to feed my worms?

Given enough bedding (wet shredded cardboard or newspaper), worms can sustain for weeks with no attention. I recommend establishing a weekly habit of adding to your worm farm, especially when you’re starting out, as it will mean you’ll be checking on them regularly, and learning about them.

Shred more cardboard or newspaper, and stir it into the worm farm. This will give worms a place to retreat and sustain while conditions in the farm settle down.

Stop feeding your worms until balance has been restored.

Should I add lime to my worm farm?

No. Liming worm farms is a popular practice, but is not necessary. Worm skin is very sensitive, and lime is an extremely alkaline material which burns them. If your worm farm is too acidic, stop feeding in scraps, and wait for the worms to regulate their environment.

Hi Maringi,
It is best to ensure your worms have plenty of bedding (shredded newspaper, cardboard, etc), and that it is moist. Then feed them a handful of scraps at a time, each time waiting until the first handful is almost gone. They will speed up slowly. Do not worry if you are feeding them too little – they will eat their bedding. If you overfeed them, you may get rotting smells. Good luck!

Thanks for your common sense approach to worm farming.
My farm is 2 years old. A recent rain has over flowed my bottom bin and all the good castings are now on the bottom with most of the worms. I have drained the bottom. The liquid smells like to bottom of a lake, so I hope with restarting the top with make everything aerobic once again.

Thanks Judy, and you’re right to be patient, as most worm farm issues resolve themselves with time. If you’re concerned about things getting too wet down there, you can always fluff it up with some shredded newspaper. Good to hear of others worm farming. I think its key to developing healthy soil.